Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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131anket Sealinq Baq Machine
Back~round of the Invention
1. Field of the Invention
This invention relates to bag fabricating machines and more
particularly to blanket sealing bag machines for the production of sealed
10 polyethylene products.
2. Descri~tion of Related Art
Prior art blanket sealing bag machines typically utilize a variable
15 diameter drum consisting of two disks of an appropriate distance apart
mounted upon a common axle. The common axle is driven by conventional
means inducing rotating motion to the axle and the two disks. Fastened to
each of the disks are equally spaced spindles, such as twelve or sixteen
spindles, which extend radially from the axle and extend to the outer
ZO diameter of the disks.
The spindles in each disk are connected to the opposing spindle on
the other disk with either a slat or a seal bar assembly. Slats, which are
mechanically joined to each of the two opposing spindles, are structural
members which define the cylindrical geometry of the sealing drum. The
2~ seal bar assemblies, fastened in a manner similar to the slats, also form the drum geometry as well as provide sealing means for placing transverse
thermal seals on the polyethylene web provided to the drum.
The drum diameter is adjustable through a motor driven means which
rotates all of the threaded spindles in the desired direction, thus lowering or
30 raisin~ the slats and seal bar assemblies relative to the drum axle. This
incre,3ses or decreases the diameter of the sealing drum. An example of a
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'~ IPEA/l~ 2 2 ~U~ 1997
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prior art blanket sealing bag machine is disclosed in U.S. Patent No.
5,447,4~,6 owned by Applicants' assignee and is incorporated herein by
reference.
The sealing process produced by the drum sealing machine may, for
5 example, be accomplished by placing a tube of polyethylene web between
the drunn geometry and a sealing blanket conforming to the external
geometry of the drum. Heat necessary for creating seals is applied through
the polyethylene web via one or more seal bar assemblies and pressure
necessary for creating seals is produced via sealing blanket tension against
~- 10 the drum. Duration of seal dwell is determined by the linear speed of the
rotating drum, the diameter of the drum, and the amount of blanket wrap
around the drum.
lrhe linear speed at which thermal webs may be sealed is dependent
upon the duration of time heat is applied to the thermal web, the amount of
15 pressure that the sealing assembly is in contact with the thermal web, and
the temperature of the sealing assembly. Temperature and pressure are
independent of the number of seal bar assemblies mounted onto the drum
and as a consequence, these values may be optimized irrespective of the
number of seal bar assemblies or the diameter of the drum. For example,
20 the temperature of the seal bar may range from three hundred fifty to five
hundred degrees Fahrenheit and the blanket sealing pressures may range
from four to five pounds per linear inch of the blanket.
Where the sealing drum comprises a given number of spindles, the
number of seal bar assemblies used is generally an integral multiplicand of
25 the given number of spindles. However, because prior art blanket sealing
bag machines have only at most twelve or sixteen spindles, seal dwell time
may olten not be optimized for a variety of desired bag lengths produced by
the machines. Specifically, a blanket sealing machine having only twelve
spindles may only have seal bar assemblies placed on one, two, three, four,
30 six, or all of the spindles (i.e., integral multiplicands of twelve) during agiven production run. Similarly, a blanket sealing machine having only
'AMENDE~ E~
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~PE~ . 2 2 AUG lgg7
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sixteen spindles may only have seal bar assemblies placed on one, two,
four, eight, or all of the spindles (i.e., integral multiplicands of sixteen)
during a given production run. Where seal time is not optimized, an
undesirable reduction in production rates may result.
rO help achieve maximum production speeds, it is desirable to
increase the multiples of seal bar assemblies by providing a seal drum
having more than sixteen spindles at each end. Where more spindles are
used, the seal drum may be larger and may also allow for more seal bar
combinations. This may allow the running of standard bag lengths on the
blankel: sealing bag machine with the drum being as large as possible in
comparison to conventional designs. Further, because the amount of
blanket wrap around the drum affects duration of seal dwell time, it is also
desirable to provide a blanket sealing bag machine having a larger angle of
blanket wrap.
Summary of the Invention
1~here is provided a blanket sealing bag machine comprising an axle,
a first plurality of spindles disposed at a first end of the axle and a like
plurality of spindles disposed at a second opposing end of the axle, the
plurality of spindles being greater than sixteen spindles, each of the
spindles extending radially from the axle, and at least one seal bar
assembly disposed on one of the spindles.
There is also provided a blanket sealing bag machine comprising an
axle, twenty four spindles disposed at a first end of the axle and twenty four
spindles disposed at a second opposing end of the axle, each of the
spindles extending radially from the axle, and at least one seal bar
assembly disposed on one of the spindles.
There is further provided a blanket sealing machine comprising a
drum and a sealing blanket assembly comprising a continuous blanket
having a.n interior portion partially disposed around the drum and an exterior
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portion providing a return path, a first blanket roller disposed at one side of
a mouth region where a web may enter between the sealing blanket
assernbly and the drum and a second blanket roller disposed at the
opposing side of the mouth region, wherein the interior portion of the
5 blanket disposed around the drum defines an angle of blanket wrap, the
angle of blanket wrap being greater than approximately two hundred three
degr~!es.
Brief DescriPtion of the Drawings
Figun~ 1 is a cross sectional view of a bianket sealing bag machine of the
present invention and further showing the seal drum with various diameters.
Figure 2 is an enlarged side view of a portion of the first tension assembly
1~ and alternate film entry paths into the sealing drum and blanket assembly.
Figure 3 is an enlarged top view of a portion of the first tension assembly.
Figure 4 is a top view of the blanket take-up roller and second tension20 assembly.
Figure ~ is an end view of the sealing drum of the present invention.
Figur~ 6 is an end view of a torque driven assembly and sealing drum and
25 blanket assembly.
iFigure 7 is a graph illustrating seal dwell time versus bag length for a
blanke~t sealing bag machine of the present invention.
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Description of the Preferred Embodiments
Referring now to Figure 1, there is shown a blanket sealing bag
o machine 10 in accordance with the principles of the present invention. Film
5 12 is provided to the blanket sealing bag machine 10 by conventional
means, not shown, such as by a set of nip rolls and dancer arrangement as
is standardly done in the industry. Alternatively, the film may be provided to
the blanket sealing bag machine 10 by a torque control assembly as
discussed below. The blanket sealing bag machine 10 provides transverse
10 he~t seals to ~he film 12 to define individual bags.
The blanket sealing bag machine 10 comprises a sealing drum 14
and a blanket assembly 16 collectively referred to as the sealing drum and
~lanket assembly 15. Furthermore, the diameter of the sealing drum is
ple~l~bly adjustable between minimum and maximum limits to increase the
15 range of possible bag lengths and to allow the seals to be imparted to the
film 12 at a desired fixed distance from any preprinted matter appearing on
the film 12. As will be described more fully hereinafter, the sealing drum 14
comprises one or more seal bars which are selectively activated depending
upon the desired length of the bags being produced and the diameter of the
20 sealing drum 14.
The blanket assembly 16 comprises a sealing blanket 18, a plurality
of blanket rollers 20, 22, 24, 26, 28, and 30, and a blanket take-up roller 32.
The sealing blanket 16 may be constructed of silicone coated polyester or
any other suitable heat resistant material and is mounted upon the plura3ity
2~ of hlanket rollers 20, 22, 24, 26, 28, and 30 as well as the blanket take-up roller 32 as shown in Figure 1.
The first blanket roller 20 is preferably not fixed to the frame 34 of
the blanket sealing bag machine 10 in order to allow an operator of the
machine to have easy access to the interior of the machine should a
30 problem arise. The first blanket roller 20 may be connected to first tension
assembly ~6. The first tension assembly 36 comprises a blanket tension
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cylinder 37 which may be a standard pneumatic cylinder manufactured by
Festo of Hauppauge, New York. The blanket tension cylinder 37 may be
secured to the frame 34 of the blanket sealing bag machine 10 via a frame
extension 39, such as a piece of steel. The first tension assembly 36 may
further comprise a cylinder rod 38. The blanket tension cylinder 37 may be
connected to the cyiinder rod 38 which may be, for example, a 20mm
diameter cylinder rod formed of steel. The opposing end of the cylinder rod
38 may be secured to a flexible coupling 40 which also forms part of the
first tension assembly 36. The flexible coupling 40 may be a rod aligning
coupling manufactured by Festo of Hauppauge, New York.
Referring also to Figures 2 and 3, the flexible coupling 40 may be
screwed into a first roller mounting bracket 42. The first roller mounting
bracket 42 is secured to a second roller mounting bracket 44 by a plurality
of bolts 46 and to a tie bar 41 by a plurality of bolts 47. The tie bar 41
extends from one side to the opposing side of the machine 10. The first
and second roller mounting brackets 42 and 44 may be formed of steel.
Two separate pairs of roller mounting brackets 42 and 44 may be used to
aid in alignment at each side of the machine and the tie bar 41 connects
the pairs together.
The second roller mounting bracket 44is secured to bearing block 43
housing linear bearings 48 which is, in turn, secured to the blanket roller 20.
The linear bearings 48 disposed at each end of the blanket roller 20 may be
INA linear bearings manufactured by Herzogenauracn of Germany. The
bearing block 43 may also be secured to an entry roll mounting bracket 50.
2~ The entry roll mounting bracket 50, which may also form part of the first
tension assembly 36, may be secured to the second roller mounting bracket
via bolts 51. The entry roll mounting bracket 50 may also have an upper
entry roll 45 and a lower entry roll 49. Use of the upper entry roll 45 and
lower entry roll 49 are optional and provide an alternate film entry path into
the sealing drum and blanket assembly 15, as best shown in Figure 2.
Either one or both of the rolls 45 and 49 may be used to alter the angle of
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entry of the film into the sealing drum and blanket assembly 15. Preferably,
the rc)ller mounting brackets 42, 44, the tie bar 41, and the entry roll
mounting bracket 50 are formed of steel.
The second roller mounting bracket 44 is slidably mounted on a shaft
~2. 1~he dimension of the shaft 52 may be, for example, 20.5 inches in
length and 50mm in diameter. The end of the shaft 52 may be secured to a
mounting bracket 54 which is, in turn, secured to a mounting bracket 56.
Mounting bracket ~6 is secured to the frame 34.
In normal operation, the blanket tension cylinder 37 is activated such
1û that the cylinder rod 38 is in its extended position. As a result, the
mounting brackets 42, 46 allow the bracket roller to be in its normal
operating condition (i.e., along the leftmost portion of the shaft 52 in the
embo~liment shown in Figure 1). When an operator wishes to view the
sealing drum 14 or blanket assembly 16, the blanket tension cylinder 37 is
deactivated. As a result, the cylinder rod 38 retracts and the bianket roller
moves rightward until the mounting bracket 44 rests against the mounting
bracket 54. Howe~fer, the first blanket roller 20 may instead be fixed in
poslbc)n.
Blanket rollers 22, 24, 26, 28, and 30 are preferably fixed blanket
2Q rollers as standardly used in the industry. The fixed blanket rollers may be
rotationally connected to the frame 34 of blanket sealing bag machine 10.
Preferably, fixed blanket rollers 22, 24, and 26 are secured to bearing
housings 62, 64, and 66, respectively, as is standardly done in the industry.
The bearing housings 62, 64, and 66 may be secured to the frame 34 of the
2~ blank~t sealing bag machine 10 by securing means such as nuts and bolts,
not shown.
Preferably blanket roller 24 is stationary and blanket roller 26 is
pivotable for blanket tracking. One end of the bearing housing 66 is
secured to a seal blanket tracking linkage 69 as is standardly used in the
indush~. The seal blanket tracking linkage may comprise two arms 70 and
71, rod end bearings 73 and 75, a mounting plate 76 comprising a plurality
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of mounting holes 77 for securing the ends of the arms 70 and 71, a
pivoting shaft 78, and a piston 72. Further, the bearing housing 66 may be
secured to a pivot plate 79 which is, in turn, connected to a linkage point 74
of the seal blanket tracking linkage 69. The seal blanket tracking linkage 69
5 helps to keep the sealing blanket 18 taut and thus allows for steering of the
blanket. Further, blanket roller 28 is preferably a mounted roller secured to
a pillow bearing block 68.
Blanket roller 30, which may be a rubber covered roll, is preferably
the driving roller. Blanket roller 30 is driven by a main drive motor 80 by
10 the use of conventional pulleys and belts, not shown. The motor 80 may be
a 5hp ac gear motor manufactured by Reliance of Cleveland, Ohio. As a
result, the sealing blanket 18is driven by the motor 80 through a drive belt
which is entrained around the fixed blanket roller 30. The contact force
between sealing blanket 18 and sealing drum 14 in turn causes sealing
1~ blanket to drive the sealing drum and thereby draw film through the blanket
sealing bag machine 10. The blanket roller 30 in the embodiment shown
rotates in a counter clockwise direction so that the film 12 travels in a
clockwise direction. As a result, the film 12 may travel from blanket roller
20 ~or from the upper entry roller 45 and/or lower entry roller 49 if either or
20 ~oth are used), around the sealing drum 14 and exit at blanket roller 30.
The blanket take-up roller 32 helps to ensure that the sealing blanket
18 is kept taut against the sealing drum 14 regardless of the diameter of the
sealing drum 14. The blanket take-up roller has bearings 90 at each end,
allowing the roller to rotate about its axis. The blanket take-up roller 32 as
2~ well as the other blanket rollers 20, 22, 24, 26, 28, and 30 are preferablysteel rollers having a diameter of approximately five-and-a-half inches.
Referring also to Figure 4, the blanket take-up roller 32 is mounted
onto a second tension assembly 92. Preferably, the second tension
assembly 92 comprises a linear rodless cylinder 94 disposed at each end of
30 the blanket take-up roller 32 as is standardly used in the industry. The
second tension assembly 92 further comprises a shaft 96, linear bearing 98,
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clevi~, plate 100, mounting plate 102, mounting block 104, shoulder bolt
106, ~nd bearing block 108. ~he rodless cyiinder 94 may be connected to
the clevis plate 100 via yokes 95 disposed on the clevis plate. Clevis plate
t 100 rnay be secured to the mounting plate 102 by bolts 97 and mounting
plate 102 may be secured to mounting block 104 by bolts 99. Bolts 101
may also secure the mounting block 104 to the bearing block 108.
Shoulder bolt 106 may be secured to the axle 103 of the blanket take-up
roller 32.
The sealing blanket 18 tension is controlled by how much pressure is
exerted on the rodless cylinders 94 disposed at each end of the machine.
The r~dless cylinders g4 exert pressure to raise or lower the blanket take-
up roller 32. Specifically, in order to keep the blanket take-up roller 32 in
equilibrium, the rodiess cylinders 94 will exert an upward or downward
force. Because the clevis plate 100, mounting plate 102 and mounting
block 104 are secured together at each end and because the clevis plate
100 at each end is attached to the rodless cylinder 94 at each end, the
mountin~T block 104 moves upward or downward in synchronization with the
clevis plate 10~ at each end. Further, because the mounting block 104 is
securing to the bearing block 108, the mounting block moves upward or
2~ down~,vard in parallel to the shaft 96 by the use of linear bearings 98 housed
in the bearing block. Moreover, because the mounting block 104 is secured
~o the axle 1~3 of the blanket take-up roller 32 by the use of shoulder bolt
1~6, the blanket take-up roller 32 moves upward or downward in
synchlronization with the force provided by the rodless cylinders 94.
2~ For example, in order for the sealing blanket 18 to be taut, there maybe a force vector of three hundred pounds exerted by the blanket take-up
roller :32 in the upward direction along the rodless cylinders 94 and two
force vectors of one hundred fifty pounds in the downward direction toward
the blanket rollers 24 and 26. The blanket take-up roller 32 will move
3~ L~pwar,d or downward should the sum of the downward force vectors not
equal the value of the upward force vector exerted on the blanket take-up
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rolier 32. That is, if the upward force vector equals two hundred ninety
pounds, then there are two force vectors of one hundred forty five pounds
in the downward direction toward the blanket rollers 24 and 26. Therefore,
the blanket take-up roller 32 is kept in equilibrium.
Where the diameter of the sealing drum 14 changes, the second
tension assembly 92 takes up the required excess or provides additional
length of the sealing blanket 18. For example, where the sealing drum 14
circumference decreases from one hundred fifty inches to sixty seven
inches, the excess of approximately eighty three inches of sealing blanket
10 18 is taken up by the web path changes and the second tension assembly
92. As a result, blanket take-up roller 32 will raise approximately 750mm.
Additionally, the tension assembly 92 helps ensure that the blanket is kept
taut by the motion of the blanket take-up roller 32. Similarly, the blanket
take-up roller 32 will lower by a similar amount if the sealing drum 14
15 circumference is increased back to one hundred hfty inches.
The first tension assembly 36 holding blanket roller 20 in place
preferably has a force which is greater than the force applied by the second
tension assembly 92 against the blanket take-up roller 32. For example,
the force applied by the first tension assembly 36 against the blanket roller
20 20 may be approximately four hundred pounds and the force applied by the
second tension assembly 92 against the blanket take-up roller 32 may be
approximately three hundred pounds. As a result, the first tension
assembly 36 effectively mounts the blanket roller 20 in a fixed position and
all movement to retain the sealing btanket 18 taut as well as taking up the
25 required excess or providing additional length of the sealing blanket 18 is
provided by the second tension assembly 92.
After passing through sealing drum and blanket assembly 15, the film
12 passes under a chill roll 110 which functions to cool the heat seals. The
chill roll 110 may be mounted to an arm 112 which is pivotally secured to
30 another arm 114. Arm 114 is, in turn, secured to the frame 34. Further, a
threaded rod 116 having a knob on top is secured to the arm 114 to adjust
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the position of the chill roll 110. The chill roll 110 may also be secured to a
tension cylinder 118 to help ensure contact between the chill roll 110 and
the filrn 12 and to allow for ease of threading of the film 12 under the chill
roll 110. Thereafter, the film 12 may be directed into a folding assembly
5 and Gl~tting assembly, not shown, as is standardly done in the bag making
indusbry for forming bags.
Referring to also to Figure 5, the sealing drum 14 is mounted on a
shaft 'd44 which is rotatably supported with bearing assemblies housed in a
bearin~ block 145 connected to the frame 34 of the bag machine. Blanket
10 rolier 3û is conventionally driven by a motor 80 which, in turn, imparts
motion to the sealing blanket 18. Because the sealing blanket 18 is in
intimate contact with the sealing drum 14, the sealing blanket 18 causes the
sealing drum 14 to rotate about the shaft 144.
The surface of the sealing drum 14 is comprised of a number of
1~ spaced apart slats 122 and seal bars 124. Although Figure 5 illustrates the
use of twenty slats 122 and four seal bars 124, any combination of slats
122 or seal bars 124 may ~e used. Preferably, where the sealing drum
comprises a given number of spindles, the number of seal bars used is an
integral multiplicand of the given number of spindles. Where more than one
20 seal l~ar 124 is used, preferably the seal bars are spaced equidistant from
one another. Slats 122 may then be placed on the remaining spindles.
~ Nhere, for example, a twenty four spindle sealing drum 14 is
ernployed (i.e., twenty four spindles at each end of the sealing drum 14),
therl a seal bar 124 may be placed on one, two, three, four, six, eight,
25 tweive, or all of the spindles (i.e., integral multiplicands of twenty four
spindles3 during a given production run. Moreover, where a thirty six spindle
sealing drum 14 is employed (i.e., thirty six spindles at each end of the
sealing drum 14), then a seal bar 124 may be placed on one, two, three,
four, si~(, nine, twelve, eighteen, or all of the spindles (i.e., integral
30 multiplicands of thirty six spindles) during a given production run. Similarly,
where an eighteen spindles sealing drum 14 is employed (i.e., eighteen
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spindles at each end of the sealing drum 14), then a seal bar 124 may be
placed on one, two, three, six, nine, or all of the spindles (i.e., integral
multiplicands of eighteen spindles) during a given production run. Slats 122
may then be placed on the remaining spindles. Where seventeen spindles
are employed, then seai bars 124 may be placed on one or all of the
spindles during a given production run. Preferably, the sealing drum 14
comprises twenty four spindles.
Conventional slats 122 and seal bars or seal assemblies 124 may be
employed on the seal drum 14. Prefera~ly, the slats are T-bar sections and
10 the seal bars are U-shaped sections extending longitudinally substantially
the width of the sealing drum. The outer surface of each slat 122 is slightly
curved and is overlaid with an appropriate rubber-type material such as
adiprene to increase the frictional force between the sealing blanket 18 and
the sealing drum 14. Each seal bar 124 also comprises an outer surface
15 overlaid with an appropriate rubber-type material such as adiprene, but in
addition comprises a longitudinal opening 130 in the outer surface through
which a heating element 132 protrudes. Each heating element 132
approximately extends the length of the seal bar 124 and is selectively
activated depending on the desired length of the bags being produced to
20 irnpart a transverse seal onto the film 12 as the film passes between the
seal bar 124 and sealing blanket 18. The ends of the slats 122 and seal
bars 124 comprises threaded blocks 134 which engage corresponding
th~eaded spindles 136. The spindles 136 are rotatably supported at each
end within yokes 138 (i.e., there are two yokes for a given spindle) secured
2~ to the side walls or disk 140 of the sealing drum 14. Preferably, the
spindles 136 are spaced equidistant from one another. Fur~her, the disk 140
may have a series of holes 142 evenly dispersed around the disk to lighten
the weight of the disk 140 in order to reduce the overall weight of the
sealing drum 14, allowing the drum to rotate more efficiently. The disks 140
30 may be secured to a shaft or axle 144 as is standardly done in the industry.
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IPEA~ 22 A~IG 1997
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The adjustability of the diameter of the sealing drum 14 is provided
through rotation of the spindles 136 which is accomplished through the
selective activation of a bi-directional motor and drive mechanism, not
shown. Preferably, the bi-directional motor is mounted on the shaft 144
5 within lhe sealing drum 14. The operation of the bi-directional motor and
drive rnechanism to change the relative position of the slats 122 and seal
bars 1.24 may, for example, be as described in U.S. Patent No. 5,447,486.
Referring back to Figure 1, the sealing drum 14 is shown having
various diameters. The sealing blanket angle of wrap preferably ranges
,;~. . 10 from approximately two hundred seventy five degrees where the sealing
drum 14 diameter is at a maximum to approximately one hundred eighty
degrees where the sealing drum 14 is at its minimum diameter. However,
preferably, the blanket angle of wrap ranges from approximately two
hundred seventy five degrees to approximately three hundred degrees
where the sealing drum is at its maximum diameter to approximately two
hundred degrees when the sealing drum is at its minimum diameter.
IBlanket roller 20 is preferably placed such that the angle of wrap is
approximately two hundred seventy five degrees to approximately three
hundred degrees when the sealing drum 14 is at its maximum diameter.
Further, the angle of blanket wrap is reduced as the sealing drum 14
diameter is reduced because the blanket rollers 20 and 30 are in a given
position.
I-or example, where the maximum circumference 150 of the sealing
drum 14 is one hundred fifty inches, the blanket angle of wrap 152 may be
two hundred seventy two degrees. Where the circumference 154 of the
sealing drum 14 is 129.25 inches, the blanket angle of wrap 156 may be
two hundred fifty degrees. Where the circumference 158 of the sealing
drum 14 is 108.5 inches, the blanket angle of wrap 160 may be two
hundrecl thirty two degrees. Where the circumference 162 of the sealing
drum 14 is 87.75 inches, the blanket angle of wrap 164 may be two
hundred seventeen degrees. Where the minimum circumference 166 is
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sixty seven inches, the blanket angle of wrap 168 may be two hundred
three degrees. Therefore, the blanket angle of wrap may, for example, be
greater than approximately two hundred three degrees, greater than
approximately two hundred seventeen degrees, greater than approximately
5 two hundred thirty two degrees, greater than approximately two hundred
fifty degrees, and greater than approximately two hundred seventy two
degrees.
As referred to above, the torque control assembly 210 for providing
the film 12 to the blanket sealing bag machine 10 may be as shown in
10 Figure 6. The torque control assembly 210 comprises torque driven means
such as torque driven rolls 214 and 216, a motor 218, and a drive 220. The
tor~ue control assembly 10 further comprises a connecting means 222.
The connecting means 222, which is preferably a timing belt, may be any
suitah,ie means for operatively connecting roll 216 to the motor 218.
The motor 218 may, for example, be a DC motor, such as a one
horsepower motor manufactured by Reliance Electric Corporation. Further,
the drive 220 may, for example, be a DC Torque Drive Series P~400
manulFactured by Danfoss Electronic Drives, a division of Danfoss, Inc.
Howe~rer, the drive 220 may be any DC, AC, or servo torque drive and the
motor may be any DC, AC, or servo motor.
The torque control assembly 210 may further comprise a torque
setting control 224 which may be connected to the control inputs of the
drive :220. The tor~ue setting control 224 is preferably a potentiometer,
such as a ten turn, hve K-Ohm, one quarter watt potentiometer. The
potenliometer 224 provides a variance in how much force or torque the
motor 228 provides to the rolls 214 and 216. Alternatively, the torque
sett~n~l control 224 may be any process level input device such as load
cells. A load cell may, for example, be placed before and after the torque
driven rolls 214 and 216 to sense the tension in the web 12 and activate the
motor 218 when too large of a tension is placed on the web 12.
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The torque controi assembly 210 may, for example, be disposed
between a pair of nip rolls 226 and dancer assembly 228 at one end and
sealing drum and blanket assembly 15 at an opposing end. The dancer
assembly 228 may comprise a plurality of conventional dancer rolls 232. A
5 plur~lity of guide rolls 248 may also be disposed between the torque control
assembly 10 and the sealing drum and blanket assembly 15.
The web 12 of plastic film is provided from a standard film supply to
the pair of nip rolls 226 and to the dancer assembly 228. The web of film
12 is disposed between the torque driven rolls 214 and 216 of the torque
control assembly 210. The web 12 is further provided to the sealing drum
and blanket assembly 15.
The web 12 of plastic film is continuously provided to the sealing
drum and blanket assembly 15. When the potentiometer 224 is set to zero,
the motor 218 may not provide any force to help the flow of the web 12 to
1~ reduce the tension in the web in the region prior to entering the sealing
drum and blanket assembly 15. The potentiometer 224 setting may
gradually be increased such that there is little or no tension in the web 12 in
the region prior to entering the sealing drum and blanket assembly 1~.
That is, when the potentiometer 224 setting is gradually increased, the drive
220 drives the motor 218 at a faster rate. This, in turn, drives the torque
d~iven r~lls 214 and 216 at a faster rate via timing belt 222. As a result, the
tension in the web 12 at the output of the torque control assembly 210
lessens. By further increasing the potentiometer 224 setting, the tension in
the web 12 at an output of the torque control assembly 210 may further
lessen such that there is little or no tension at the output of the torque
control assembly 210.
In a typical application, 200ms of seal dwell time may be required in
order to properly seal a polyethylene film 12. Therefore, if the seal dwell
time is greater than that figure, then the blanket sealing bag machine may
~e operated at a higher speed. Referring now to Figure 7, there is shown a
plot o~ seal dwell time versus bag length for various operating speeds for a
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blanket sealing bag machine constructed in accordance with the principles
of the present invention whose variable circumference ranges from sixty
seven to one hundred fifty inches. As seen, the blanket sealing bag
machine may produce an appropriate seal even where the film is moving as
5 fast as eight hundred feet per minute.
It should be recognized that, while the present invention has been
described in relation to the preferred embodiments thereof, those skilled in
the art may develop a wide variation of structural details without departing
from the principles of the invention. Therefore, the appended claims are to
1~ be construed to cover all equivalents falling within the true scope and spirit
of the invention.
